R&D: Sensitivity Analysis on Fatigue Life of SSD Solder

Microsystem Technologies has published an article written by Yeungjung Cho, Jinwoo Jang, and Gunhee Jang, PREM, Department of Mechanical Convergence Engineering, Hanyang University, Seoul, Korea

Abstract: “We proposed a method to determine the probabilistic fatigue-life distribution of solid state drives (SSDs) due under thermal cycling through finite element method and Monte Carlo simulation and the effect of their design and operating variables on failure through sensitivity analysis. In the developed finite element model, we utilized the Anand model to represent the viscoplastic behavior of solder balls and utilized the Prony series to represent the viscoelastic behavior of a polymer material in the underfill. In order to verify the developed finite element model, we compared the simulated strain with that measured in a thermal chamber. Using the developed finite element model, thermal cycling analysis was performed to determine the fatigue life of the SSD using the simulated results and Morrow’s energy-based fatigue model. The finite element analysis results showed that the outermost solder ball at the corner of the dynamic random access memory (DRAM), was the most vulnerable component under thermal cycling. Monte Carlo simulation was performed to analyze the fatigue life distribution according to the manufacturing tolerances of the design and operating variables of the SSD. Sensitivity analysis was also performed to determine the effects of variables on number of cycles to failure. The analysis results showed that the minimum temperature of the thermal cycling profile condition and the diameter of the DRAM solder balls dominantly affected the fatigue life of the SSD.“